Plasma ablation treatment

It is important to emphasize that O2 plasma treatment collects much more F-containing contaminants on the alloy surface than without O2 plasma treatment, although this treatment virtually eliminated the interference of the contaminants to the subsequent TMS deposition as described in the previous section. In other words, O2 plasma treatment does not reduce the amount of fluorine on aluminum alloy surface but reduces plasma-ablatable fluorine on aluminum alloy surface. 

Plasma pre-treatment has been the subject of much research with a wide variety of polymers. In this method, power is applied to a gas or a monomer at low pressure (typically 1 torr) and a plasma, consisting of ions, electrons, atoms and free radicals, is formed. Improved adhesion may be due to a variety of mechanisms including ablation of small molecules, cross-linking or introduction of functional groups such as carbonyl and amine. With monomers, such as acrylates, grafting to the polymer surface can occur. 

The parameters of treatment were chosen since these led to the most pronounced changes of polymer surface in our previous experiments [70-74]. It was observed elsewhere that plasma treatment of polymer macromolecules results in their cleavage, ablation, alterations of chemical structure and thus affects surface properties e g. solubility [75]. The chemical structure of modified polyethylene (PE) was characterized by FTIR and XPS spectroscopy. Exposition to discharge leads to cleavage of polymeric chains and C-H bonds followed by generation of free radicals which easily oxidize [10,76]. By FTIR spectroscopy the presence of new oxidized structures within whole specimen volume can be detected. IR spectra in the 1710-1745 cm" interval [71,77] from PE, exposed to... 

The creation of reactive species that cause ablation is essentially the same process as that occurs in LCVD, except that the final result is completely opposite, i.e., ablation vs. deposition. In this context, ablation by luminous gas could be described as luminous chemical vapor treatment (LCVT). Therefore, the dependence of ablation on operational parameters in LCVT is very similar to that of LCVD, which is discussed in more detail in Chapter 4. The chemical ablation of polymeric materials by O2 plasma [6] is described here to demonstrate how oxidative ablation is influenced by the operational parameters of discharge. 

The decrease of Si due to F-containing contaminants and the role of the oxygen plasma treatment can be explained by the principle of CAP. The key factor to explain the change of elementary composition at the interface is the plasma sensitivity of elements involved on the surface and in the plasma phase. The ablation of materials exposed to plasmas appears to follow the plasma sensitivity series of the elements involved, which is in the order of the electronegativity of the elements, i.e., elements with higher electronegativity in the condensed phase are more prone to ablate in plasma that contains elements with lower electronegativity [5]. 

While there have been several promising research outcomes reported on animal studies, it would require much more systematic studies on the consequences and side effects of the APP before adopting the non-thermal APP treatment to actual clinical studies. As a side note, the classical argon plasma coagulation (APC) device, which is a type of thermal plasma of a high temperature, has been used as a surgical tool as a comparable tool to the laser ablator or electrical scalpel [10, 72, 73], but we leave this out to the references because it is beyond the scope of this chapter. 

Plasma treatment of microchannels can be useful for improving the functionality of microdevices. For example, previous studies have shown that PDMS microchannels can be made hydrophilic by the addition of silane molecules with polar head groups [6]. In this process (3-mercaptopropyl)trimethoxysilane (3-MPS) was absorbed to PDMS to increase the hydrophilic properties of microchannels. Additionally, plasma polymerization has been used to induce in the long-term hydrophilic surface modification by covalently bonding a polymer layer to the surface. Barbier et al. [7] describe a method based on plasma polymerization modification with acrylic acid coatings. First, argon plasma pretreatment was used to activate trace oxygen molecules in the chamber, which partially oxidize the top layer of the substrate. This step cross-linked the surface to reduce ablation of silicon... 

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